My 5yo daughter and I were scanning through the Lego Catalog to see what Lego set we could buy, when she spotted Emma's Horse Trailer.
When we bought the set, I was expecting that I would have to build the set for my child but the instructions were laid out exceptionally well. This set is recommended for 6+ but my 5yo had no trouble putting it together with just a little assistance from her dad.
It's a great set as once it's built, your child is guaranteed to have hours of fun. I highly recommend it to any parent who wants their child to learn to put a lego set together themselves.